Mars Water Traces Left by Springs, Not Seas, Experts Say

Scott Norris
for National Geographic News
March 7, 2007
Curious deposits on Mars that originally appeared to be signs of an ancient ocean were instead produced by water emerging from underground, experts say.

A new study has found that networks of springs and a shallow water table can account for mineral deposits first discovered by the Mars rover Opportunity in 2004.

The deposits had been considered possible evidence that extensive lakes or oceans once existed for long periods on the Martian surface before finally evaporating.

The new study concludes that while the region where the deposits were found, known as Meridiani Planum, may at times have contained rivers and ponds in low-lying areas, it was no sea bed (see Mars map).

"Meridiani is one of the few regions of the planet where groundwater would be expected to reach the surface and evaporate to leave behind deposits of salts and evaporite minerals [minerals formed by the evaporation of water]," said lead author Jeffrey Andrews-Hanna, of the Massachusetts Institute of Technology.

His team's study appears in tomorrow's edition of the journal Nature.

Underground River

The researchers used data on Martian topography and geology to model the likely distribution and movement of subsurface water over hundreds of millions of years.

The model shows that water may have traveled distances of up to 621 miles (1,000 kilometers) deep underground before finally spilling out at Meridiani.

The results coincide with other findings, including satellite photographs showing networks of fractured rock through which underground water once flowed

(Read related story: "New Mars Pictures Show Signs of Watery 'Aquifers'" [February 16, 2007].)

Steve Squyres, principal investigator for the Mars rover missions, said the new study "squares very well with both rover and orbital results."

"There is no closed basin at Meridiani, and so formation of significant evaporite deposits there requires that it be a region of groundwater upwelling," Squyres said.

Andrews-Hanna said the finding does not imply that oceanlike bodies of water were never present on Mars.

"Large amounts of water on the surface of Mars were certainly possible early in the planet's history," he said.

But as the planet dried, he said, "water would have been present only where the global-scale groundwater flow brought the water table to the surface."

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